Subscribers use various devices (e.g., a cellular telephone or pager) to communicate with other subscribers within a satellite communication system. These devices communicate with the system via several communications processes, each involving an exchange of messages between the subscriber and the system.
Registration, for example, is one of these communication processes. Each registration process involves an exchange of registration messages between the subscriber and the system. Registration may also be used to keep track of the subscriber so that the system knows where to send messages that indicate an incoming call for that subscriber.
Call setup is another example of these communication processes. Each call setup process involves an exchange of a set of call setup messages between the subscriber and the system. These messages may also contain registration messages.
Hand-off is a process that occurs during the course of either a call or a registration process. The hand-off process is used to transfer the call from the coverage of one cell or beam to another.
In some existing satellite systems, provision has been made to allow isolated local networks supporting more than one fixed telephone set to access such satellite communication systems. Typically, a multiple-user communication unit (MCU) is used to couple a local network to a satellite communication system. A mobile exchange unit (MCU) provides, among other things, an interface between a local network and a satellite communication system. Typically, the MCU supports multiple channels to the satellite communication system, and the MCU allows individual users of the local network access to the satellite communication system by allowing the multiple channels to be shared by the subscribers associated with the local network.
Procedures for allowing multiple-user communication devices to access the communication system should efficiently use system resources. In some cases, these local networks are generally large enough that it is either economically or physically impossible to allocate a radio access resource to each fixed telephone set. In other cases, these isolated local networks are on mobile vehicles where individual communication units are not easily supported.
The impact on a communication system of multiple subscribers using multiple-user communication devices is particularly trouble-some when groups of subscribers, which are using a particular MCU, request service at the same time or within a short period of time. This can occur on a mobile vehicle (e.g., communication units on-board an airplane). In this case, all of the system subscribers might request registration when they board the airplane and the MCU has to individually register each subscriber with the system.
As a part of typical cellular call processing procedures, each subscriber registers, hand-offs, and setups a call individually with the system. The impact of high load transients upon the system results in a large amount of work which has to be performed by the system in a relatively short amount of time. However, since systems are typically constrained to the number of processes it can perform in a given time period, such an impulsive load of processes can detrimentally affect the system. This may cause other system subscribers that are also requesting service to be queued behind a large processing load, leading to an increased number of dropped calls and dissatisfied system subscribers.
Thus, what is needed are a method and apparatus for reducing impulsive loading of a communication system. What is also needed are a method and apparatus for reducing impulsive loading by groups of subscribers who are using a multiple-user communication unit. Further needed is a method and apparatus to reduce the amount of work which a communication system has to perform to provide services to groups of subscribers.